In numerous applications, V-belt drives are used to transmit power from the shaft of a motor to another mechanism, e.g., a fan or blower. In many of these applications, the power output level requires two or more V-belts to be used. In others, the motor is used to power two or more separate mechanisms which, in turn, requires two or more V-belts. In such situations, multiple groove pulleys are generally used. However, in some of these situations, one or more of the driven mechanisms may require a speed ratio which is not provided by a readily available multiple groove pulley of fixed pitch diameter. In those situations, multiple groove variable pitch pulleys have been suggested and used in the past.
For example, U.S. Pat. Nos. 2,633,031 to Browning, 2,855,787 to Kumro et al., 2,890,592 to Keepers and 3,661,023 to Maurey all disclose variable pitch pulleys having a single stationary center flange with an adjustable flange mounted on each side of the center flange. These pulleys are thus limited by design to two belt-receiving grooves.
U.S. Pat. No. 3,063,300 to Chung discloses a multiple groove variable pitch pulley system having a hub with two separate sets of threads. An end flange is mounted at one end of the hub and an annular center flange and sleeve are threaded onto the hub engaging the first set of threads. An annular second end flange, having a bore for receiving the sleeve of the center flange, is then threaded onto the hub, engaging the second set of threads.
U.S. Pat. Nos. 3,214,986 to Anderson et al. and 3,782,211 to Campbell et al. each discloses multiple groove, variable pitch pulleys wherein the belt-engaging grooves are formed by two sets of annular members, one set which can be moved simultaneously relative to the first set which is fixed.
The pulley systems above tend to be overly complex, difficult to adjust and/or have limited versatility. Accordingly, there is a need for a simple, yet versatile and easily adjustable multiple groove pulley system.